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| United States Patent |
6,232,250
|
|
Palumbo
, et al.
|
May 15, 2001
|
Absorbent article
Abstract
An article for absorbing fluid includes a fluid-storage region and a fluid
receiving region. The fluid receiving region releases fluid to the fluid
storage and has a dry laid web of staple fibers with a high bulkiness. The
article may be used for treating female incontinence.
| Inventors:
|
Palumbo; Gianfranco (Pescara, IT);
d'Ambrosio; Antonio (late of Pescara, IT);
Carlucci; Giovanni (Chieti, IT)
|
| Assignee:
|
The Procter & Gamble Company (Cincinnati, OH)
|
| Appl. No.:
|
553706 |
| Filed:
|
August 7, 1997 |
| PCT Filed:
|
June 3, 1994
|
| PCT NO:
|
PCT/EP94/01814
|
| 371 Date:
|
August 7, 1997
|
| 102(e) Date:
|
August 7, 1997
|
| PCT PUB.NO.:
|
WO94/28838 |
| PCT PUB. Date:
|
December 22, 1994 |
Foreign Application Priority Data
| Jun 04, 1993[IT] | T093A0402 |
| Current U.S. Class: |
442/389; 428/156; 428/171; 428/913; 442/414; 442/415; 604/368; 604/378 |
| Intern'l Class: |
B32B 005/08; B32B 005/12 |
| Field of Search: |
604/378,368
428/913,156,171
442/389,414,415
|
References Cited
U.S. Patent Documents
| 3881489 | May., 1975 | Hartwell | 604/369.
|
| 3929135 | Dec., 1975 | Thompson | 604/385.
|
| 3989867 | Nov., 1976 | Sisson | 428/132.
|
| 4578414 | Mar., 1986 | Sawyer et al. | 524/310.
|
| 4761258 | Aug., 1988 | Enloe | 264/518.
|
| 4904249 | Feb., 1990 | Miller et al. | 604/378.
|
| 5147343 | Sep., 1992 | Kellenberger | 604/368.
|
| 5364382 | Nov., 1994 | Latimer et al. | 604/378.
|
| 5429629 | Jul., 1995 | Latimer et al. | 604/378.
|
| 5591149 | Jan., 1997 | Cree et al. | 604/378.
|
| 5913850 | Jun., 1999 | D'Alessio | 604/378.
|
| Foreign Patent Documents |
| 0 018 020 | Oct., 1980 | EP.
| |
| 0 018 684 | Nov., 1980 | EP.
| |
| 0 059 506 | Sep., 1982 | EP.
| |
| 108637 | May., 1984 | EP.
| |
| 0 207 904 | Jan., 1987 | EP.
| |
| 306262 | Mar., 1989 | EP.
| |
| 532005 | Mar., 1993 | EP.
| |
| WO 9111165 | Aug., 1991 | WO.
| |
| WO91/14733 | Oct., 1991 | WO.
| |
| WO91/15368 | Oct., 1991 | WO.
| |
| WO91/15362 | Oct., 1991 | WO.
| |
| WO91/14734 | Oct., 1991 | WO.
| |
| WO93/04093 | Mar., 1993 | WO.
| |
| WO93/04092 | Mar., 1993 | WO.
| |
| WO93/04113 | Mar., 1993 | WO.
| |
| WO93/04115 | Mar., 1993 | WO.
| |
| WO93/03699 | Mar., 1993 | WO.
| |
| WO94/26834 | Nov., 1994 | WO.
| |
Primary Examiner: Morris; Terrel
Assistant Examiner: Guarriello; John J.
Attorney, Agent or Firm: McDermott, Will & Emery
Claims
What is claimed is:
1. An article for absorbing fluid, which comprises, successively from a
first face thereof to an opposite face, a fluid-permeable topsheet (1), a
fluid-receiving region (6), a fluid-storage region (7), and a
fluid-impermeable backsheet (2), the fluid-receiving region being formed
of a dry laid web of staple, permanently hydrophilic, synthetic fibers,
the web having a bulkiness, as measured under a pressure of 2 kPa, of at
least 15 cm.sup.3 /g, and a thickness of from 1 to 10 mm, the
fluid-receiving region being adapted to release to the fluid-storage
region at least 99% of the fluid which it receives, wherein 100% of the
fibers of the fluid-receiving region are bicomponent fibers, each fiber
comprising a polypropylene portion, and a portion which has a surface
exposed to the exterior of the fiber and which is formed of a polyethylene
resin with a wetting agent incorporated therein.
2. An article according to claim 1, wherein the said bulkiness is not more
than 65 cm.sup.3 /g.
3. An article according to claim 2, wherein the said bulkiness is from 20
to 60 cm.sup.3 /g.
4. An article according to claim 3, wherein the said bulkiness is from 25
to 55 cm.sup.3 /g.
5. An article according to claim 4, wherein the said bulkiness is from 30
to 50 cm.sup.3 /g.
6. An article according to claim 1, wherein the said thickness is from 1.5
to 6 mm.
7. An article according to claim 6, wherein the said thickness is from 1.7
to 4.5 mm.
8. An article according to claim 7, wherein the said thickness is from 2 to
4 mm.
9. An article according to claim 1, wherein the basis weight of the
material of the said fluid-receiving region is from 25 to 300 g/m.sup.2.
10. An article according to claim 9, wherein the said basis weight is from
40 to 200 g/m.sup.2.
11. An article according to claim 10, wherein the said basis weight is from
50 to 180 g/m.sup.2.
12. An article according to claim 1, wherein the material of the said
fluid-receiving region has a wet collapse value of not more than 45%, as
measured by the wet collapse test method described herein.
13. An article according to claim 12, wherein the said wet collapse value
is not more than 40%.
14. An article according to claim 1, wherein the material of the said
fluid-receiving region has a wet resilience value of not more than 40%, as
measured by the wet resilience test method described herein.
15. An article according to claim 14, wherein the said wet resilience value
is not more than 25%.
16. An article according to claim 15, wherein the said wet resilience value
is not more than 25%.
17. An article according to claim 1, wherein the material of the said
fluid-receiving region has a wetting time of not more than 5 seconds, as
measured by the wetting time test method described herein.
18. An article according to claim 17, wherein the said wetting time is not
more than 2 seconds.
19. An article according to claim 1, wherein the material of the
fluid-receiving region is formed using fibers having a diameter not more
than 40 .mu.m.
20. An article according to claim 19, wherein the said diameter is from 15
to 20 .mu.m.
21. An article according to claim 1, wherein the said fluid-storage region
comprises an absorbent hydrogel material.
22. An article according to claim 21, wherein the said fluid-storage region
further comprises a cellulose material.
23. An article according to claim 21, wherein the said absorbent hydrogel
material is in particulate form.
24. An article according to claim 1, wherein the said fluid-storage region
comprises a laminate having outer layers of cellulose-containing material
and an intermediate layer of absorbent hydrogel material.
25. An article according to claim 1, wherein the said fluid-storage region
comprises a laminate having outer layers and a central layer of
cellulose-containing material, and two further layers of absorbent
hydrogel material respectively between the central layer and the two outer
layers.
26. An article according to claim 1, wherein the said fluid-receiving
region is in the form of a sheet, and the said fluid-storage region is in
the form of a further sheet in face-to-face relationship with the
fluid-receiving sheet.
27. An article according to claim 26, wherein the said fluid-receiving
sheet and the said fluid-storage sheet are secured to one another by an
adhesive.
28. An article according to claim 1, wherein the topsheet and backsheet are
sealed to one another around the periphery thereof.
29. An article according to claim 28, the article having a thickness, when
dry of t.sub.d, and a thickness, when wetted to its maximum extent, of
t.sub.w, with t.sub.w >t.sub.d, the topsheet and backsheet being sealed
together along respective edge portions thereof, and the topsheet having a
fluid permeable central area, and a fluid impermeable area adjacent the
sealed edge portion thereof, the size of the fluid impermeable area being
such that, even when the article is wet to its maximum extent, the fluid
permeable area of the sheet is not in communication with at least a major
portion of the edges of the fluid-receiving sheet.
30. An article according to claim 1, shaped to form a pad suitable for
incontinent females.
31. An article according to claim 1, in the form of an absorbent pad for
use by a user suffering from incontinence, the pad having a thickness when
dry of t mm, as measured with the pad under pressure of 2 kPa, a fluid
storage capacity of s ml and the ability to receive gushes at an average
rate, as measured over three successive equal gushes totalling G (ml), of
up to g ml/sec, where
s/t.gtoreq.8 ml/mm; and
g/t.gtoreq.0.1 ml/mm. sec
at least for some value of G/s.gtoreq.2/3.
32. An article according to claim 31, wherein g/t.gtoreq.0.2 ml/mm. sec.
33. An article according to claim 32, wherein g/t.gtoreq.0.3 ml/mm. sec.
Description
This invention relates to an absorbent article. It is particularly
concerned with an absorbent article, for example in the form of a pad,
which can be used by women suffering from light and moderate incontinence.
The invention will be so described below. However, the invention is of
more general applicability in relation to the absorption of body fluids,
either urine or menstrua. It can therefore be used, for example, in the
manufacture of infant diapers, and in incontinence products for adults, in
addition to the incontinence product specifically identified above.
A condition of light incontinence exists in many women. An absorbent pad,
or other article, for use by those with this condition should desirably
(a) Be thin, and with a shape fitting well into the underpants, to provide
discretion when worn under normal clothing.
(b) Be absorbent enough to handle large quantities of urine.
(c) Absorb rapidly enough to accept the surge of urine (gush handling) that
can occur from women who have this condition, and maintain this capability
even through multiple gushes.
Research indicates that 10-20% of the female population suffer from light
involuntary urine losses. The magnitude of the problem varies from losing
just a few dribbles in special situations (coughing, sneezing, during
sports) to a more serious, permanent problem (after menopause or in
conjunction with gynaecological operations). The product selected by such
women, and the usage frequency, depends on the seriousness of the problem:
pantiliner usage with 1-2 changes per day for occasional urine losses
moving to a higher change frequency (2-8 pantiliners/day) for higher
loadings and/or more frequent bladder weakness. For those at the upper end
of the problem range, pantiliners are not sufficiently absorbent, besides
being prone to bunching and to disintegration during use, and such women
use 2-3 catamenial pads per day.
Existing products for light incontinence are similar to oversized thick
catamenial pads. Most are very thick, about 15 mm thick, and this does not
provide the degree of discretion the user desires. Furthermore, these
products have absorbent cores that typically collapse when wetted, thus
making them deficient in fluid absorption rate for subsequent loadings.
For the lightest conditions of light incontinence, many women use standard
pantiliners. These products provide the desired level of discretion under
clothing; however, they are totally inadequate in absorbency. Part of this
deficiency is in absorbent capacity, but more important is the deficiency
in absorbent rate.
One object of the present invention is to provide an absorbent article for
dealing with light and moderate incontinence, which is discrete, has the
absorbent capacity required, and has the necessary gush handling ability.
According to one aspect of the present invention there is provided an
article for absorbing fluid, which comprises a fluid-storage region and a
fluid-receiving region adapted to release fluid to the fluid-storage
region, the fluid-receiving region being formed of a dry laid, for example
an airlaid, web of staple fibers, the web having a bulkiness, as measured
under a pressure of 2 kPa, of at least 15 cm.sup.3 /g.
By "staple fibers" we mean fibers which are not continuous, and which may
be synthetic fibers, natural fibers, or a mixture of synthetic and natural
fibers.
It is believed that the high bulkiness of the fluid-receiving region is
such that the fluid is free to flow with very little impedance by the
fibers defining the region. This is in contrast to the approach adopted in
known products dealing with incontinence, where any fluid-receiving region
serves as a wick to transfer fluid received at one part of the region to
other parts thereof. However, it is to be understood that this explanation
is offered here as a suggestion only, and no categorical assertion is made
that it is correct.
Preferred features of the fluid-receiving and fluid-storage regions are
described below and are set out in the sub-claims.
The article preferably further comprises a water-permeable top sheet in
face-to-face relationship with the said fluid-receiving sheet, on the
opposite side thereof to the fluid-storage sheet, and a water-impermeable
backsheet in face-to-face relationship with the fluid-storage sheet, on
the opposite side thereof to the fluid-receiving sheet.
The topsheet and backsheet are preferably sealed to one another, and the
article shaped to form a pad suitable for incontinent females.
According to another aspect of the invention there is provided an absorbent
pad for use by a user suffering from incontinence, which comprises a
fluid-storage layer, and a fluid-receiving layer adapted to receive fluid
from the user and release it to the fluid-storage layer, the pad having a
thickness when dry of t mm, as measured with the pad under pressure of 2
kPa, a fluid storage capacity of s ml and the ability to receive gushes at
an average rate, as measured over three successive equal gushes totalling
G (ml), of up to g ml/sec, where
s/t.gtoreq.8 ml/mm; and
g/t.gtoreq.0.1 ml/mm. sec;
at least for some value of G/s.gtoreq.2/3.
Preferably g/t.gtoreq.0.2 ml/mm. sec., more preferably .gtoreq.0.3
ml/mm/sec.
According to yet another aspect of the invention there is provided an
article for absorbing fluid, which comprises a fluid-storage region, a
fluid-receiving region adapted to release fluid to the fluid-storage
region, a fluid-permeable topsheet in face-to-face relationship with the
said fluid-receiving sheet, on the opposite side thereof to the
fluid-storage sheet, and a fluid-impermeable backsheet in face-to-face
relationship with the fluid-storage sheet, on the opposite side thereof to
the fluid-receiving sheet, the article having a thickness, when dry, of
t.sub.d, and a thickness, when wetted to its maximum extent, of t.sub.w,
with t.sub.w >t.sub.d, the topsheet and backsheet being sealed together
along respective edge portions thereof, and the topsheet having a fluid
permeable central area, and a fluid impermeable area adjacent the sealed
edge portion thereof, the size of the fluid impermeable area being such
that, even when the article is wet to its maximum extent, the fluid
permeable area of the sheet is not in communication with at least a major
part of the edges of the fluid-receiving region.
The absorbent article can be thin, being as little as 3 mm in thickness, or
even less, and provided it has the correct contours to fit well into
underwear can be highly discreet. The key is that the article swells only
when heavily wetted. This is in contrast to existing products on the
market, which if they provide anything approaching an acceptable level of
absorbence, are bulky even when dry.
In the accompanying drawings:
FIG. 1 is a plan view of an embodiment of an absorbent article according to
the present invention; and
FIG. 2 is a diagrammatic cross-section, on a larger scale, through the
crotch region of the article shown in FIG. 1.
The embodiment of FIGS. 1 and 2 comprises a liquid permeable topsheet 1 and
a liquid impermeable backsheet 2 sealed to one another along a peripheral
region 3 thereof by, for example, thermal bonding. The backsheet 2 has a
layer 4 of hot-melt adhesive coated thereon, to which is attached a
release sheet 5 which is removed by the user before use. Within the
enclosure defined by the topsheet 1 and backsheet 2 there is provided a
secondary sheet 6, adjacent to topsheet 1, and an absorbent storage core
7. The sheet 6 and core 7 are attached to one another by a layer 8 of cold
glue. The layer 8 is discontinuous, so that liquid can pass from the sheet
6 to the core 7.
The layer 8 is preferably of the type disclosed in our copending Italian
Patent Application No. T093A 000338 filed on May 17, 1993 and entitled
"Adhesive composition, related methods and use". The copending application
describes a water-based adhesive composition comprising a blend of
adhesive polymers in an aqueous system, characterised in that the blend of
adhesive polymers is:
20-60% by weight of an acrylic polymer having a polarity balance expressed
as water absorption according to DIN 53495 of 3 to 20%; and
correspondingly
40-80% by weight of a compatible tackifying resin having a degree of
hydrophobicity measured as the contact angle between a dried film of the
resin and a drop of distilled water of not less than 60.degree.;
the percentages being based on the total of acrylic polymer plus tackifying
resin expressed as dry solids.
The layer 6 is attached to the topsheet 1 by a plurality of narrow stripes
9 of hot-melt adhesive. The core 7 is attached to the backsheet 2 by a
layer 10 of hot melt adhesive.
It can be seen that the core 7 consists of three layers, namely upper and
lower layers 11 and 12 each of a cellulose-based material, and a middle
layer 13 of a water-insoluble hydrogel material. At the edges of the layer
13 are lines of adhesive 14 which serve to confine the hydrogel material
and prevent liquid therein leaking out.
The absorbent article will now be described in more detail with reference
to the four layers thereof.
1. Topsheet
The top layer (user side) is a topsheet that must be comfortable to the
touch, provide a dry feeling over an absorbent core filled with liquid,
and pass fluid rapidly into the interior of the core. It is liquid
permeable in the central longitudinal zone and is liquid impermeable at
least in the two lateral zones in order to handle totally the urine during
the gush, while avoiding lateral leakage. The width of the liquid
impermeable area is such that even when the article is wet to its maximum
extent, and is correspondingly swollen, the fluid permeable area of the
sheet is not in communication with the lateral edges of the
fluid-receiving secondary sheet. This avoid lateral leakage from the core.
The liquid impermeable area may extend completely around the liquid
permeable area.
This element can be of a variety of known materials, for example: a) a
formed-film topsheet as described in U.S. Pat. No. 3,929,135, or any of
European Patent specifications Nos. EP-A-0018020, EP-A-0018684 and
EP-A-0059506, (b) a partially perforated fiber/film composite described in
EP-A-207904, the perforated area thereof providing a liquid permeable
area, and the unperforated area thereof providing a liquid impermeable
area, or (c) a nonwoven film produced by the spunbonding or by a carded,
thermal-bonded process, or a sheet produced by various other processes
currently practised.
2. Secondary Sheet
This element has the characteristics of accepting a high rate of fluid
intake, serving as a temporary reservoir for the fluid, and then draining
substantially completely into the storage core in order to remain empty
for subsequent fluid loadings. In addition, this element must resist
collapse when wet so that it maintains its performance through multiple
loadings. This element must do all these things while also remaining
extremely thin. An airlaid web of synthetic fibres can be used for this
purpose. The secondary sheet should preferably have hydrophilic
properties.
The secondary sheet preferably has the following characteristics:
(a) A thickness of from 1 to 10 mm, more preferably from 1.5 to 6 mm, still
more preferably from 1.7 to 4.5 mm, and even more preferably from 2 to 4
mm, the thickness being measured with the sheet under a pressure of 2 kPa.
(b) A basis weight of from 35 to 300 g/m.sup.2, more preferably from in
excess of 40 up to 40 to 200 g/m.sup.2, still more preferably from 42 or
43 to 200 g/m.sup.2, and yet more preferably from 50 to 180 g/m.sup.2.
Typically, it may be up to 150 cm.sup.3 /g. For example, basis weights of
45, 60, 80 and 120 g/m.sup.2 have been used and found to be satisfactory.
(c) As already mentioned, the sheet has a bulkiness of at least 15 cm.sup.3
/g, when the sheet is under a pressure of 2 kPa. More preferably, the
bulkiness is from 15 to 65 cm.sup.3 /g, still more preferably from 20 to
60 cm.sup.3 /g, and yet more preferably from 25 to 55 cm.sup.3 /g. It may
advantageously be from 30 to 50 cm.sup.3 /g. Desirably, the minimum value
for the bulkiness is 32, 33, 34 or 35 cm.sup.3 /g.
(d) The ability to discharge to the storage core at least 95%, and more
preferably at least 99% of the fluid which it receives in a loading.
(e) A wet collapse at 2.7 kPa of not more than 45%, and more preferably not
more than 40%.
(f) A wet resilience at 0.1 kPa of not more than 40%, more preferably not
more than 30%, and still more preferably not more than 25%.
(g) A wetting time of not more than 5 seconds, and preferably not more than
2 seconds.
(h) It is formed of fibres having a diameter of not more than 40 .mu.m,
preferably not more than 20 .mu.m, and still more preferably from 15-20
.mu.m, and a length of not more than 20 mm, preferably not more than 12
mm, and most preferably about 6 mm.
3. Storage Core
The third layer is a thin, high-capacity absorbent core. While thin when
dry, this element of the structure preferably expands when wetted to
provide a high, tenacious fluid-holding ability, and it must avoid
collapse when wet. The storage core is itself preferably formed of a
plurality of layers. For example, a three layer structure may be used in
which the outer layers are of a cellulose tissue material (and may be the
same as, or different from, one another). The middle layer is of a
water-insoluble hydrogel, which is a polymeric material in particulate
form, capable of absorbing a large quantity of liquid and retaining it
under moderate pressures.
It is important that the secondary sheet and the storage core work
together. In particular, given the form of secondary sheet used herein, it
is possible in this structure to avoid the typical problem of gel blocking
in the storage core, because the secondary sheet provides total
distribution of the fluid, and then drains it into the storage core
whenever the storage core has not yet received fluid.
As an alternative to the form of storage core described above, it can be
one of a number of thin, high-capacity materials. For example, the storage
core can be a sheet of fused AGM particles as described in International
Patent Applications Nos. WO91/14733, WO91/14734, WO91/15362 and WO91/15368
or a high capacity foam, as described, for example, in International
Patent Publications Nos. WO93/04092, WO93/03699, WO93/04093, WO93/04113
and WO93/04115.
4. Impervious Backsheet
The backsheet is impervious to liquids and, thus, prevents fluid which may
be expressed from absorbent core from soiling the body or clothing of the
user. Suitable materials are well known in the art, including woven and
nonwoven fabrics which have been treated to render them liquid repellent.
Breathable or vapour pervious, liquid resistant materials, and those
materials described in U.S. Pat. No. 3,881,489 and U.S. Pat. No. 3,989,867
can also be used. Preferred materials are those materials that are fluid
and vapour impervious, because they provide additional fluid strikethrough
protection. Especially preferred materials include formed thermoplastic
films.
EXAMPLE 1
The topsheet is partially perforated fiber/film composite coverstock of the
type described in EP-A-0207904. It is partially perforated over a
rectangular area which runs lengthwise and centrally of the pad and which
has a width of 38 mm.
The secondary sheet is formed using a hydrophilic resin from Dow Chemical
called ASPUN (CODE XU 61518.11) which is a polyethylene resin containing a
wetting agent, of the type described in U.S. Pat. No. 4,578,414.
Polyethylene itself is inherently hydrophobic. Bicomponent crimped fibers
are formed incorporating this wettable resin. The fibers comprise a
polypropylene portion and a portion which is formed of the wettable resin
mixed with LLDPE (linear, low density polyethylene). At least the latter
portion has at least part of its surface exposed to the exterior of the
fiber. The fibers are thus rendered permanently hydrophobic. The fibers
are cut into staple fibers 6 mm in length, and the staple fibers are
airlaid to form a resilient web of wholly synthetic, hydrophilic fibers.
The fibers have a diameter of about 18 .mu.m. The process of airlaying
includes the step of applying heat or an adhesive to cause those fibers
which touch, or almost touch, one another to bond to each other and those
points. Preferably, at least the major part of the fibers of the secondary
sheet are the bicomponent fibers, and more preferably substantially 100%
are, and most preferably 100% are.
The properties of the secondary sheet thus formed, using 100% bicomponent
fibers, and using thermal bonding, are given in the following table under
the heading Element 2. By way of comparison, the second column gives the
properties of a secondary sheet used in an existing product sold for light
incontinence by Kimberly Clark Corporation under the name Poise Pads R.A.
For the purpose of the comparison test, a secondary sheet was removed from
a Poise pad.
Poise Pad R.A.
Element 2 2nd Sheet
Basis Weight (g/m.sup.2) 60 130
Caliper (mm @ 2 kPa pressure) 2.3 1.6
Bulkiness (cc/g) @ 38.3 12.3
2 kPa pressure)
Dunk capacity (g/g/ @ P = 0) 36.5 20.6
Fluid Retention (g/g) 0.01 1.5
Fluid % discharge* 99.97 92.72
Wet Collapse (% loss @ 2.7 37.1 48.7
kPa)
Wet Resilience (% loss @ 0.1 17.7 42.5
kPa)
Wetting Time (sec) 0.2 7.2
*Fluid % discharge = (Dunk capacity - Fluid Retention)/Dunk capacity
.times. 100.
The table above demonstrates the superiority of the secondary sheet used in
the invention in each of a number of important performance areas.
The high bulkiness demonstrates that it has a high void volume, and has the
ability to acquire fluid efficiently.
The wetting time demonstrates the wettability of the web.
The low fluid retention value demonstrates the ability of the secondary
sheet to drain the fluid almost completely (give up fluid into the storage
core beneath it), so that the secondary sheet drains completely into the
storage core and is therefore available for subsequent loadings.
The low wet collapse and low wet resilience values show that neither the
capillary forces of fluid inside the structure, nor external pressure
loadings, cause a harmful loss of the open void volume required for the
structure to perform well.
The dunk capacity describes the property of being filled substantially
totally with urine.
The storage core is a three-layer structure laminate, having the following
layers:
a) A top layer having a weight of 75 g/m.sup.2, of dry-formed,
thermal-bonded, cellulose tissue with bicomponent polyolefin staple
fibers. The latter are polyethylene-polypropylene ES-C fibers from
Danaklon A/S, with a denier of 1.7 dtex and a length of 6 mm, the fibers
consisting of polypropylene with a polyethylene sheath.
b) Middle layer of particulate (100-800 micron) polyacrylate AGM (absorbent
gel material) Dow XZ type (200 g/m.sup.2);
c) Bottom layer of air-laid, latex-bonded cellulose embossed tissue (55
g/m.sup.2).
Alternatively, the structure may be made according to our Italian Patent
Application No. TO 93 A 001028, which has similarities to what is
described in TO 92 A 000566, but which incorporates an AGM material in a
higher basis weight.
This structure is made according to Italian Patent Application TO 92 A
000566.
The backsheet is a 25 .mu.m coextruded polypropylene/polyethylene film.
The dimensions and weights of Example 1 are set out in Table 1 below.
TABLE 1
Basis Surface/
Length weight Grams/ pad
Material (mm) Width (mm) (g/m.sup.2) pad (cm.sup.2)
ABSORBENT 140 42 338 1.95 57.80
CORE
Top Layer 140 42 75 0.43
Middle Layer 140 35 200 0.97
Bottom Layer 140 42 55 0.32
TOPSHEET 153 67 (widest) 38 0.327 84.843
(partially 51
perforated: (narrowest)
38 mm)
SECONDARY 140 40 60 0.347 57.80
SHEET
BACKSHEET 153 67 (widest) 24 0.204 84.843
51
(narrowest)
Pad dimensions 153 67 (widest) Pad weight: 3.38 g
51
(narrowest)
Pad caliper 3.1 mm @ 2 kPa
3.9 mm @ 0.2 kPa
The absorbent pad of Example 1 is intended for use by someone suffering
very light incontinence in which each fluid discharge averages about 5 ml
and a gush rate of 15 ml/sec. The pad has an absorbent capacity in excess
of 20 ml.
EXAMPLES 2 TO 4
These are largely identical to Example 1, except for differing dimensions
and weights. These are set out in Tables 2 to 4 below which apply,
respectively to Examples 2 to 4. However, as appears from Tables 3 and 4,
in Examples 3 and 4 the absorbent core consists of five layers rather than
three, to provide greater absorbent capacity. The top and bottom layers
correspond to the top and bottom layers of Examples 1 and 2. The second
and fourth layers are of an AGM material similar to the middle layer in
Examples 1 and 2, and the third layer is of an airlaid, non-woven material
identical to the bottom layer.
Example 2 is intended for someone for whom the average discharge is about
15 ml at a gush rate of 15 ml/sec. It has an absorbent capacity in excess
of 40 ml. Example 3 is intended for someone for whom the average discharge
is about 25 ml and at a gush rate of 20 ml/sec. It has an absorbent
capacity in excess of 100 ml. Example 4 is intended for someone for whom
the average discharge is about 50 ml and at a gush rate of 20 ml/sec. It
has an absorbent capacity in excess of 150 ml. Examples 1 to 4 are
sufficient between them to cover the needs of virtually all lightly or
moderately incontinent women.
TABLE 2
Basis Surface/
Length weight pad
Material (mm) Width (mm) (g/m.sup.2) Grams/pad (cm.sup.2)
ABSORBENT 180 57 364 3.68 101.01
CORE
Top Layer 180 57 75 0.758
Middle Layer 180 50 200 1.800
Bottom Layer 180 57 55 0.556
TOPSHEET 210 90(widest) 38 0.619 160.70
partially 75
perforated: (narrowest)
44 mm)
SECONDARY 180 50 60 0.538 89.74
SHEET
BACKSHEET 210 90(widest) 24 0.386 160.70
75
(narrowest)
Pad dimensions 210 90(widest) Pad weight: 6.276 g
75
(narrowest)
Pad caliper 3.6 mm @ 2 kPa
4.1 mm @ 0.2 kPa
TABLE 3
Basis Surface/
Length weight Grams/ pad
Material (mm) Width (mm) (g/m.sup.2) pad (cm.sup.2)
ABSORBENT 216 54 560 6.562 116.64
CORE
Top Layer 216 54 75 0.875
Second Layer 216 46 150 1.490
Third Layer 216 54 55 0.642
Fourth Layer 216 46 215 2.136
Bottom Layer 216 54 55 0.642
TOPSHEET 252 102 (widest) 38 0.822 216.39
(partially 78
performated: (narrowest)
54 mm)
SECONDARY 234 84 (widest) 90 1.438 159.77
SHEET 60
(narrowest)
BACKSHEET 252 102 (widest) 24 0.519 216.39
78
(narrowest)
Pad dimensions 252 102 (widest) Pad weight: 10.19 g
78
(narrowest)
Pad caliper 5 mm @ 2 kPa
TABLE 4
Basis Surface/
Length weight Grams/ pad
Material (mm) Width (mm) (g/m.sup.2) pad (cm.sup.2)
ABSORBENT 260 65 560 9.456 169.00
CORE
Top Layer 260 65 75 1.267
Second Layer 260 57 150 2.223
Third Layer 260 65 55 0.929
Fourth Layer 260 57 205 3.038
Bottom Layer 260 65 55 0.929
TOPSHEET 301 122 (widest) 38 1.173 308.68
(partially 93
perforated: (narrowest)
54 mm)
SECONDARY 283 104 (widest) 130 3.126 240.5
SHEET 75
(narrowest)
BACKSHEET 301 122 (widest) 24 0.741 308.68
93
(narrowest)
Pad dimensions 301 122 (widest) Pad weight: 15.51 g
93
(narrowest)
Pad caliper 7 mm @ 2 kPa
The performance of Examples 1 and 2 versus existing products was evaluated
in an acquisition test and a rewetting test. The way in which these tests
are carried out is set out below, and the results are given in Tables 5
and 6.
TABLE 5
Core Composition Theoretical Acquisition Time
Thick Fibers AGM Capacity (sec)
Rewetting
Product (mm) (g) (g) (cc) 1st 2nd 3rd (g)
Always 4 1.7 0.8 29 6 22 28 0.0
Ultra
Normal
Poise Pad 17 9.7 2.4 106 3 23 42 0.5
R.A.
Carefree 3 1.5 6 6 18 Leaked
Leaked
Example 1 3.1 0.7 1.0 31 4 7 9 0.6
TABLE 6
Core Composition Theoretical Acquisition Time
Thick Fibers AGM Capacity (sec)
Rewetting
Product (mm) (g) (g) (cc) 1st 2nd 3rd (g)
Always 4 1.7 0.8 29 10 59 Leaked
Leaked
Ultra
Normal
Poise Pad 17 9.7 2.4 106 4 41 49 0.1
R.A.
Poise Pad 17 10.5 4.5 168 4 61 72 0.6
E.A.
Serene 5-12 4.4 0.7 37 8 33 Leaked
Leaked
10 cc Min-
(Kobayashi) Max
Example 2 3.6 1.3 2.0 61 7 14 16 1.3
In the test of Table 5 there are 3 loadings each of 7 ml of fluid (21 ml
total) at a rate of 20 ml/second. In Table 6 there are 3 loadings of 15 ml
(45 ml total) at a rate of 20 ml/second. The word "leaked" indicates that
because of leakage from the product a meaningful rewet value could not be
obtained. CAREFREE is a Trade Mark used for pantiliners. ALWAYS ULTRA
NORMAL is a Trade Mark used for catamenial pads. POISE PAD R.A., POISE PAD
E.A. and SERENA are Trade Marks used for light incontinence products.
Under the heading "CORE COMPOSITION", the term "fibers" denotes the weight
of the cellulose-based part of the core and the term "AGM" denotes the
weight of the absorbent gel material. The theoretical capacity is
calculated as Fiber weight.times.4+AGM weight.times.28.
Some of the results of Tables 5 and 6, together with some additional
results, are presented below in Table 7 in a somewhat different form. This
shows the following values:
t (mm): thickness of article when dry, under a pressure
of 20 g/cm.sup.2.
s (ml): theoretical fluid capacity of the article.
G (ml): total volume of fluid applied to the article in
three equal gushes separated by 10 minute
intervals.
time (sec): total of the three times taken for the three
gushes to be absorbed.
g/t: gush absorbance rate per mm thickness, where the
gush absorbent rate g = G (ml)/time (sec).
TABLE 7
t (mm) s (ml) s/t G (ml) time (sec) g/t
Example 1 3.1 31 10 21 20 0.339
Carefree 3 6 2 21 leaks --
Always Ultra 4 29 7.2 21 56 0.094
Normal
Poise R.A. 17 106 6.2 21 68 0.018
Example 2 3.6 61 16.9 45 37 0.338
Always Ultra 4 29 7.2 45 leaks --
Normal
Poise R.A. 17 106 6.2 45 94 0.028
Poise E.A. 17 168 9.9 45 137 0.019
Serena 10 cc 5-12 37 4.35* 45 leaks --
Example 3 5 118 23.6 100 38 0.526
Example 4 7 156 22.3 150 25 0.857
*Calculated assuming an average thickness of 8.5 mm
It will be seen that the value of g/t is substantially greater for the
Examples according to the invention than for the prior art comparisons,
showing a much greater rapidity in absorbing fluid in relation to their
thickness. Also the value of s/t is greater, showing a greater total
ability to absorb in relation to their thickness. It will be observed that
the tests were carried out using three different sizes of gush, having
regard to the fact that the products being tested were of different sizes.
It can be seen that there is a degree of comparability in the Tests, at
least as regards the Examples according to the invention, in that for all
of them the value of G/s lies in a range of from 2/3 to 1 (0.68 for
Example 1, 0.74 for Example 2, 0.85 for Example 3 and 0.96 for Example 4).
Two further examples are set out in Tables 8 and 9 below. Both are intended
for use by someone suffering very light incontinence in which each fluid
discharge averages about 5 ml and a gush rate of 15 ml/sec. In each case
the pad has an absorbent capacity in excess of 20 ml.
TABLE 8
Basic Surface/
Length weight Grams/ pad
Material (mm) Width (mm) (p/m.sup.2) pad (cm.sup.2)
ABSORBENT 140 37 347 1.80 51.80
CORE
Top Layer 140 37 75 0.39
Middle Layer 140 29 200 0.81
Bottom Layer 140 37 55 0.28
TOPSHEET 165 70 (widest) 38 0.377 99.317
55
(narrowest)
SECONDARY 150 57 (widest) 60 0.428 71.270
SHEET 42
(narrowest)
BACKSHEET 165 70 (widest) 24 0.238 99.317
55
(narrowest)
Pad dimensions 165 70 (widest) Pad weight: 3.523 g
55
(narrowest)
Pad caliper 3.1 mm @ 2 kPa
3.9 mm @ 0.2 kPa
TABLE 9
Basic Surface/
Length weight Grams/ pad
Material (mm) Width (mm) (p/m.sup.2) pad (cm.sup.2)
ABSORBENT 180 45 390 3.16 81.00
CORE
Top Layer 180 45 75
Middle Layer 180 37 220
Bottom Layer 180 45 55
TOPSHEET 210 85 (widest) 38 0.572 150.51
(partially 65
perforated: (narrowest)
44 mm)
SECONDARY 194 69 (widest) 60 0.667 111.09
SHEET 51
(narrowest)
BACKSHEET 210 85 (widest) 24 0.361 150.51
65
(narrowest)
Pad dimensions 210 85 (widest) Pad weight: 5.654 g
65
(narrowest)
Pad caliper 3.6 mm @ 2 kPa
4.1 mm @ 0.2 kPa
One variation of what is described above is to use two layers of the
secondary topsheet material rather than one. These layers can be held
together if required by a liquid-permeable adhesive layer.
The following sets out the methods used to measure various parameters
mentioned above:
Dunk Capacity
This method evaluates the free absorption capacity of the material. A
rectangular sample of material 25.4.times.100 mm is put onto the surface
of a liquid (synthetic urine, of which the composition is given below) and
left on it for one minute. It is then withdrawn by means of a metallic net
and left to drip in horizontal position for one minute.
The dunk capacity is obtained as:
(Wet weight-dry weight)/dry weight of the sample (g/g).
Fluid Retention
The samples obtained from the above test method are rotated in a centrifuge
under a g-force of 240 g for ten minutes.
The fluid retention is obtained as:
(Wet weight-dry weight)/dry weight of the sample (g/g).
Wet Collapse
The samples 38.times.50 mm are made of as many superimposed layers of
material as are needed to get an overall basis weight of 500 g/m.sup.2.
The samples are wetted in the same was as in the dunk capacity test. They
are then placed on a perforated plexiglass plate and subjected to three
dynamic cycles of compression and decompression (speed of the pressing
head 10 mm/min, maximum load for each cycle 2.7 kPa). The minimum
thickness of the sample under compression is measured.
The wet collapse is:
(initial thickness-minimum thickness/initial thickness of the
sample).times.100(%).
Wet Resilience
In the above described test the final thickness of the sample after the
last decompression is measured.
The wet resilience is then obtained as:
(initial thickness-final thickness)/(initial thickness).times.100(%).
Wetting Time
In this test, samples of the secondary sheet of the present invention and
samples of the second sheet of Poise Pad R.A. having the same volume of
about 5 cc are compared. The considered thicknesses correspond to the
calipers under pressure (see the values on the table). The samples are
placed horizontally onto the surface of water by means of a metallic net.
The wetting time is the time needed for each sample to get completely
soaked.
Acquisition Test
This method evaluates the time required for the acquisition of given
amounts of liquid during repeated imbitions (three in this case), at a
high speed (20 ml/sec) and under a low pressure (2.7 kPa).
Each product is laid down on a flat surface and an acquisition plate is
placed on it. The acquisition plate comprises a rectangular plexiglass
plate 70.times.220.times.8 mm with an aperture 22 mm in diameter formed
therein. A cylinder 45 mm high and 22 mm in internal diameter is located
over the aperture in sealing contact with the plate. The cylinder is
filled with synthetic urine to which a dye has been added and a pressure
of 2.7 kPa is applied to the plate, obtained with appropriate weights
positioned on the plate, the pressure being that measured with reference
to the portion of the product under the acquisition plate. The acquisition
time is the time from the beginning of each imbition until the
disappearance of the liquid from the interior of the cylinder. A waiting
time of 10 minutes is left after each imbition before repeating the
procedure.
Rewetting Test
10 minutes after the last imbition in the acquisition test the acquisition
plate is removed and ten sheets of absorbent paper (220 g/m.sup.2 each)
are positioned over the product. A plexiglass plate (180.times.60 mm) is
put onto the absorbent paper and the portion of the product under the
plate is then subjected to a pressure of 5.9 kPa. The amount of liquid
absorbed by the absorbent paper is taken as the rewetting value for each
sample.
Composition of the Synthetic Urine Used in the Tests
The synthetic urine is a solution in distilled water containing the
following salts (in weight percent):
Urea 2%, sodium chloride 0.9%, magnesium sulphate (heptahydrate) 0.11%,
calcium chloride 0.06%.
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